A variety of conventional techniques for adjusting light transmittance have been introduced.
First, one example thereof is a technique for adjusting light transmittance using polymer dispersed liquid crystal (PDLC). The polymer dispersed liquid crystal controls transmission of light according to a scattering intensity of the light. When no voltage (i.e., electric field) is applied thereto, the direction of molecules of the liquid crystal becomes irregular to generate scattering on an interface having a refractive index different from that of the medium, so that the light transmittance is decreased. When a voltage is applied thereto, the direction of the liquid crystal becomes regular to make the refractive indices the same at the interface, so that the light transmittance is increased. However, according to the above conventional technique, there occurs a problem that when attempting to realize a transparent state by applying a voltage, it is difficult to achieve high light transmittance close to 100% due to the light scattering caused by the liquid crystal. There also occurs a problem that when the thickness of cells is not great, contrast cannot be ensured, consequently increasing a driving voltage.
Next, another example is a technique of adjusting light transmittance using a suspended particle device (SPD). According to this technique, light transmittance is adjusted by applying an electric field to control the arrangement of particles dispersed in a liquid. However, according to the above conventional technique, there occurs a problem that it is difficult to achieve high light transmittance close to 100% due to the particles extensively dispersed in the liquid.
Next, yet another example is a technique of adjusting light transmittance using an electrowetting display (EWD). According to this technique, light transmittance may be controlled by applying an electric field to a first liquid including a light blocking agent (e.g., a dye or the like) and a second liquid not being mixed with the first liquid to control the wettability between the first liquid and a substrate. However, according to the above conventional technique using the electrowetting display, light is blocked using a dye dispersed in a liquid and it is difficult to reliably block the light only with the dye, which causes a problem that increase in the degree of the light blocking is limited and an optical density (OD) is also low. Further, there occurs a durability problem, for example, that the dye is degenerated by infrared light or the state of a substrate surface is repeatedly changed (e.g., from hydrophilic to hydrophobic or vice versa) so that the reproducibility of the surface state is reduced.
Next, still another example is a technique of adjusting light transmittance using an electrophoretic display (EPD). According to this technique, light transmittance may be adjusted by applying an electric field to charged particles to move the particles and adjusting the degree of light blocking by means of the moved particles. However, according to the above conventional technique, the moving speed of the particles is not sufficiently high due to the movement resistance of the particles in a solvent, which causes a problem that the operation of adjusting the light transmittance becomes slower.
In this regard, the inventors of the present invention have conceived a method for adjusting light transmission, which may accelerate the switching of light transmittance, increase an optical density, and achieve high light transmittance close to 100%, as well as a device for adjusting light transmission and a method for manufacturing the same.